1. Field of the Invention
A common problem with liquid spraying devices of the hand-operated type is the need for relief of the negative pressure created in the closed container on which the device is used as liquid is pumped. The vacuum created is relieved by venting atmospheric air into the container to displace the liquid dispensed. Various ways to do this have been proposed in the art and, in general, usually involve separate or discrete value means with or without a vent passage, and more often than not, are difficult to construct and are expensive. In addition, prior art devices are often cumbersome to use and operate.
It is also very important that the device not leak when the trigger or actuator is at rest and the container and sprayer are laid on a side or even inverted such as might be the case in normal use in spraying or in shipment where a full container might be supplied with the device when sold.
2. Description of the Prior Art
A number of patents have been issued on trigger-piston type hand sprayers useful for dispensing liquid from containers. For example, a particularly useful, and perhaps the basic, trigger type sprayer is disclosed in U.S. Pat. No. 3,061,202, issued on Oct. 30, 1962 to Tracy B. Tyler wherein venting is provided by means of a separate valve biased in the normally open position. Other patents disclosing similar sprayers also using discrete valve means for venting are U.S. Pat. No. 3,650,473, issued on Mar. 13, 1972 to Carl E. Malone, U.S. Pat. No. 3,685,739, on Aug. 22, 1972 to Vance R. Vanier, and U.S. Pat. No. 3,780,951, on Dec. 25, 1973 to Richard T. Powers. The first mentioned Malone patent vents in a manner similar to the Tyler device while the patent to Powers shows an atmospheric vent through the body of the sprayer where it attaches to the container but has a collar which is screwed down by the operator into an annular slot to close it off and thus prevent leakage of liquid from the container. Second mentioned patent to Vanier utilizes a vent passage which allows atmospheric air to flow through the sparyer's lower body past a resilient, conically-shaped hollow valve into the container.
In U.S. Pat. No. 3,840,157, issued on Oct. 3, 1974 to J. F. Hellenkamp, a trigger operated sprayer is disclosed which differs from the sprayers of the aforementioned patents in that a plunger, or piston is mounted with its axis vertically aligned and movable off a sealing collar to permit venting of a container and is an example of a lever or trigger operated vent device, as is U.S. Pat. No. 3,749,290, issued on July 31, 1973 to L. A. Micalleff, which discloses a deformable diaphragm pump system wherein a venting surface is unseated to permit atmospheric pressure to be applied to the interior of the container. Other patented devices having venting means are U.S. Pat. No. 3,701,478, issued Oct. 31, 1972, U.S. Pat. No. 3,762,647, issued Oct. 2, 1973 and U.S. Pat. No. 3,770,206, issued Nov. 6, 1973 to T. Tada; U.S. Pat. No. 3,768,734, issued Oct. 30, 1974 to I. O. Anderson, Jr., et al.; and U.S. Pat. No. 3,820,721, issued on June 28, 1974 to J. F. Hellenkamp.
The present invention provides a simple, efficient, relatively inexpensive and easy to use venting system and includes an automatic drain back feature in a pleasantly appearing structure which operates during pumping and spraying and without the empolyment of additional parts or component mechanisms.